Grace K. Charles

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Large mammalian herbivores (LMH) strongly influence plant communities, and these effects can propagate indirectly throughout food webs. Most existing large-scale manipulations of LMH presence/absence consist of a single exclusion treatment, and few are replicated across environmental gradients. Thus, important questions remain about the functional roles of(More)
Large herbivorous mammals play an important role in structuring African savannahs and are undergoing widespread population declines and local extinctions, with the largest species being the most vulnerable. The impact of these declines on key ecological processes hinges on the degree of functional redundancy within large-herbivore assemblages, a subject(More)
Oxidized analogs of cholesterol (oxysterols) are produced through both enzymatic and non-enzymatic pathways and have been shown to perturb membrane properties in vitro and in vivo. In the present study, the membrane behavior of two naturally occurring oxysterols, 25-hydroxycholesterol and 7-ketocholesterol, was examined in two model systems. The presence of(More)
Plant communities in abiotically stressful, or 'harsh', habitats have been reported to be less invaded by non-native species than those in more moderate habitats. Here, we synthesize descriptive and experimental evidence for low levels of invasion in habitats characterized by a variety of environmental stressors: low nitrogen; low phosphorus; saline, sodic(More)
Male ornamentation is assumed to have evolved primarily from selection by female mate choice. Yet this is only one possible reason for ornament evolution. Ornaments might also be useful in aggressive competition by improving opponent assessment between males, or they might function to enhance signal detection by making males more conspicuous in the(More)
Animals communicating socially are expected to produce signals that are conspicuous within the habitats in which they live. The particular way in which a species adapts to its environment will depend on its ancestral condition and evolutionary history. At this point, it is unclear how properties of the environment and historical factors interact to shape(More)
Many plants provide predatory arthropods with food or shelter. Glandular trichomes entrap insects and may provision predators with insect carrion, though it has not been clear whether this putative benefit functions with natural amounts of carrion, whether plants actively attract insect "tourists," and how common this provisioning system is. We tested the(More)
Gossypol showed primary antimitochondrial activity in yeast cells in that the drug (1) inhibited growth of cells utilizing mitochondrial substrates as carbon and energy sources, and (2) selectively inhibited mitochondrial protein synthesis. Primary antimitochondrial activity was demonstrated in guinea-pig keratinocytes (GPK) by early arrest of growth and(More)
delta 7-5-Desaturase catalyses one of the last steps in ergosterol biosynthesis in fungi. Moreover delta 5-unsaturation is necessary for the sparking function. Synthesis of three pairs of C-6 epimeric cholestanol derivatives are described as potential growth inhibitors. Preliminary results suggest that 6 beta-aminocholestanol is a potent antifungal agent.